LTM4607 operation

Question

Hi, could you please provide some insight into LTM4607 operation? 
 What will happen if the external feedback resistor value is selected so low that the output will try to go above 25V? Is the absolute maximum rating of Vout=25V something that the part limits it to, or is this something the design has to make sure does not happen? 
 In my case the input voltage is 28V. The reason I'm asking this question is that I need to have the output voltage (or current) controlled digitally, so I wanted to use a feedback loop instead of the resistor (providing 0.8V on Vfb pin in steady state). 
 Thanks in advance, 
 Alexander

MarkusHP · Accepted Answer

Hello, 
 my first guess (without knowing all internal details) is the 25V voltage rating of the output cap (CO1 in figure 1 page 8) As the LTM4607 is a module the PowerFETs, inductor and capacitors are 'real' discrete devices with their own characteristic. 
 So configuring the part for operation beyond absmax is nothing we can recommend as it will lowers the part lifetime. The LTM4607 will no limit its output voltage on its own (or maybe once by destroying himself). 
 For your planned application i would recommend our LTC7106/-1 current DAC as optimal choice for adjusting DC/DC output voltages. 
 Your system/software should be configured that absmax/datasheet limits are obeyed by the circuitry.)

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LTM4607 operation